Method of manufacturing an airway device

ABSTRACT

An airway device for human or animal use comprising an airway tube having a distal end and a proximal end, the distal and of which is surrounded by a laryngeal cuff, adapted to fit anatomically over the laryngeal structure of a patient, wherein the device optionally further comprises a buccal cavity stabilizer located on or around the airway tube between the laryngeal cuff and the proximal end of the tube, said buccal cavity stabilizer being adapted to nest with the anterior aspect of the patient&#39;s tongue, the size, shape and configuration of the buccal stabilizer being adapted to prevent rotational or side-to-side movement of the airway device in use.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/983,199, filed Nov. 5, 2004 now U.S. Pat. No. 8,215,307, which is acontinuation-in-part of PCT International Patent Application Serial No.PCT/GB2003/003577, filed Aug. 14, 2003, designating the United States.Priority is also claimed from PCT International Patent ApplicationSerial No. PCT/GB2004/003481, filed Aug. 13, 2004 and European UtilityDesign Application Serial Nos. 000180757, filed May 7, 2004 and000197124, filed Jun. 24, 2004.

FIELD OF THE INVENTION

This invention relates to an anatomically oriented, simple butversatile, improved airway device. It is particularly applicable, but inno way limited, to devices used in the administration of anaesthetics toa patient breathing spontaneously during a surgical procedure. Thepresent invention relates in particular to a laryngeal airway device.More specifically, the present invention relates to reduced cost,disposable laryngeal airway device, and to methods of fabricating suchairway device.

BACKGROUND TO THE INVENTION

Examples of devices currently used in spontaneously breathinganaesthetized patients, during recovering after anaesthetics, weaning ofa certain group of patients in intensive care, or during resuscitationto provide a clear and hands-free airway are:—

-   a) Guedel airway with various types of face masks.-   b) Cuffed Oro-pharyngeal airway.-   c) Laryngeal Mask Airway (LMA), reinforced LMA, intubating LMA and a    modified Intavent LMA for ENT and dental anaesthesia.-   d) Airway Management device.-   e) Combi-tube.-   f) Self-retaining nasopharyngeal airway.-   g) Cuffed or non-cuffed Endotracheal tubes, R.A.E. endotracheal    tube.-   h) Supraglottic oropharyngeal airway.-   i) Tracheostomy and mini-trache tubes.-   j) etc etc

All of the above mentioned devices carry significant and varying degreesof co-morbidity involving not only unacceptable concurrent physiologicalchanges but also temporary and/or permanent anatomical/structuraldamage. Many cases of mortality caused directly or indirectly as aresult of the use of such devices have also been reported.

Probably the most successful design variant is the inflatable laryngealairway device, variants of which have been used to administeranaesthetic gases since 1988.

A brief history of the development of such airway device is described ina review by A I J Brain in the European Journal of Anaesthesiology 1991,Supplement 4, pages 5 to 17 inclusive. The entire text of this review ishereby incorporated by reference and is intended to form an integralpart of this disclosure.

If the respiratory tree is seen as a tube terminating at the glottis,and the objective is to make a simple connection between this tube andan artificial tube for supplying gas under low pressure to the bronchialtree, it would seem logical to form a direct end-to-end junction betweenthe two tubes. The face mask forms an end-to-end junction indeed, butwith the wrong orifice, while the endotracheal tube meets the correctorifice but goes too far by penetrating into the lumen, so that thejunction is effected within it, instead of at its rim. The undesirableaspects of intubation of the trachea result from the fact that, toeffect a seal, pressure is applied to an epithelial surface whoseimportant and highly specialized functions are thus compromised and thatby penetration of the vocal cords, effective coughing is renderedimpossible, upper-airway architecture is distorted and unwanted reflexresponse are not only provoked by laryngoscopy needed prior tointubation but also by presence of endotracheal tube in the trachea.Such laryngeal masks have been used in anaesthetic practice since 1988and many reports of co-morbidity and/or mortality directly or indirectlyrelated to their use have been reported. Complications and/or morbidityare caused by hyperinflation and extraluminal pressure impact onto thesoft tissue and cartilagenous structures in contact with thehyperinflated cuff.

Several attempts have been made to improve this type of airway devicebut they still suffer from a number of serious inherent drawbacks.Firstly, they require inflation of the cuff to be effective andfurthermore anaesthetic gas (nitrous oxide) can diffuse into the cuff,expanding the air in the cuff, thus increasing the cuffs extraluminalpressure significantly, and as a result, put considerable pressure onthe sensitive tissues of Laryngopharynx. Secondly, these masks have atendency to move from side to side or rotate about their longitudinalaxis as a force is applied to the proximinal end of the tube, attachedto the anaesthetic equipment. It will be appreciated that if such adevice is to lie perfectly symmetrically in use then the airway tubewill be aligned with the patient's nose. However, any rotational orsideways movement of the airway tube will have the potential to affectthe seal that the airway device makes around the laryngeal inlet.

Several types of airway device have been described in the patentliterature. For example, U.S. Pat. No. 5,976,072 (Johns HopkinsUniversity) describes a fiberoptic endotracheal intubation device.However, this relies on an inflatable oro-pharyngeal cuff that suffersfrom the disadvantages referred to above.

U.S. Pat. No. 5,865,176 (O'Neil) and GB2,319,182 (VBM MedizintechnikGmbH) describe airway devices having a double inflatable cuffarrangement, a first inflatable cuff for providing a seal in thepatient's pharynx and a second inflatable cuff for providing a seal inthe patient's oesophagus. This arrangement compounds the problem oftissue damage as set out above.

In a contrasting arrangement, GB2,373,188 (Smiths Group plc) describesan inflatable laryngeal mask with a tear-shaped blocker plate designedto prevent the mask blocking the epiglottis during insertion. This onlygoes to emphasise the potential downsides of a tubular inflatable maskof this type.

Finally, in WO00/61213 (Brain) there is described a disposable laryngealmask airway device with an inflatable cuff. However, not only does thissuffer from all the disadvantages of an inflatable cuff device, but itis formed from multiple components, adding to the cost and complexity ofmanufacture.

Collectively, these represent the closest prior art known to theapplicant.

It is an object of the present invention to overcome or mitigate some orall of these problems.

It is a further object of the present invention to provide an airwaydevice that is both simple and effective to use and cost-effective tomanufacture.

Where a single use item is concerned, cost of manufacture, andminimising this cost, is important. A further objective of the presentinvention is therefore to provide cost-effective methods formanufacturing airway devices that enable the unit cost per item to beminimised.

It is also an object of this invention to satisfy the requirements ofclinical situations where a buccal cavity stabiliser would not enhance,but impede the operation. For example in many ophthalmalogical, andmaxillofacial or dental surgery situations the use of a reinforced tubeis preferable, as the tube can flexibly moved to one side to continue toprovide an airway for the patient, whilst not interfering with theoperation.

In summary, where it might be advantageous to have an airway device witha buccal cavity stabiliser in some applications, we have discovered thatthere are several applications where this is disadvantageous. In factthere are several applications where it is just not practical to have abuccal cavity stabiliser.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides an airway device asdescribed in the accompanying claims.

Accordingly, according to a first embodiment, there is provided anairway device for human or animal use comprising an airway tube having adistal end and a proximal end, the distal end of which is surrounded bya laryngeal cuff, characterised in that the laryngeal cuff is adapted toform an anatomical fit over the laryngeal inlet of a patient, and tocover and form a substantially gas-tight seal with the laryngeal inletof the patient, the device further comprising a buccal cavity stabiliserlocated on or around the airway tube between the laryngeal cuff and theproximal end of the tube, said buccal cavity stabiliser being adapted tonest with the anterior aspect of the patient's tongue, the size, shape,softness and configuration of the buccal stabiliser being adapted toprovide stability and to prevent rotational or side-to-side movement ofthe airway tube in use. This buccal cavity stabiliser may be formed fromthe same material as the cuff or from a different material and assistsin locating and maintaining the position of the device in use.

Airway devices according to the present invention will be referred to inthe following text by the shorthand abbreviation NLA (Nasir LaryngealAirway Device), named after the inventor.

Preferably the cuff is non-inflatable and is pre-formed in a shapeadapted to form an anatomical fit over the laryngeal framework of apatient. The aryepiglotlic fold, arytenoid & corniculate cartilages.Interarytenoid fold and piriform fossae make the laryngeal structureanatomically an irregular structure. The terms laryngeal inlet,laryngeal framework and laryngeal structure are used interchangeably inthe following description. These terms relate to the larynx area of apatient and the surrounding tissue, folds and cartilages as illustratedin FIG. 1.

The device is a mirror image of the laryngopharyngeal framework thusproviding an anatomical fit to the irregular structural framework of thelaryngopharynx. Incorporation of an anatomically designed cup/cuff alsooffers advantages over the use of an inflatable cuff which will exert asignificant extra luminal pressure not only well beyond the pressure(22-26 mm/Hg) at which the soft tissue surface is being supplied butwill also distort, compress, dislocate, dislodge or fracture thestructures in contact with the cuff. Extraluminal pressure is exertedonto the structure of laryngopharynx not only by the cuff's repeatedinflation with air to create an adequate seal, which is achieved at thecost of distortion of the surrounding structures by undue pressurecaused by a rounded, smooth-faced tensed cuff, and also increased insitu by absorption of nitrous oxide (anaesthetic gas) into the cuff'slumens. This can increase cuff pressure beyond 100 mmHg immediately,rising beyond 200 mmHg within an hour's use, which is well above thenormal intracellular pressure or the pressure at which the bloodcapillaries supply the laryngopharyngeal structures.

Preferably the laryngeal cuff is pre-formed, pre-inflated with air orpre-filled with a suitable fluid.

Preferably the face of the laryngeal cuff adapted to form an anatomicalfit over the laryngeal framework of a patient incorporates protuberancesdesigned to form a good seal with the pyriform fossae and aryepiglotticfolds of the laryngeal framework of the patient. It is also preferredthat the face of the laryngeal cuff incorporates protuberances designedto form a good seal with the valleculae, epiglottis, aryepiglotticfolds, pyriform fossae and around the anterior aspect of thyroid &cricoid cartilages. The seal around these features may also bereinforced or enhanced by one or more feather-like flanges locatedaround part or all of the perimeter of the laryngeal cuff. This designenables increased seal pressure that will allow well in excess of 30 cmH₂O to be obtained.

In a further preferred embodiment the face of the laryngeal cuff adaptedto fit snugly over the laryngeal inlet of a patient incorporates groovesdesigned to allow passage of vital arteries, veins and nerves supplyingthe laryngeal structure.

In a particularly preferred embodiment the distal tip of the laryngealcup is so sized and shaped as to remain above the upper oesophagealsphincter in use. Most preferably the distal tip of the laryngeal cup issubstantially concave in shape.

In an alternative embodiment the laryngeal cup portion is pre-formedfrom a material which is adapted to absorb a liquid such aswater/mucous/blood or similar matter to swell to conform to theanatomical mucocartilagenous framework of laryngeal inlet e.g. materiallike CRM (cotton rayon mix)—used to manufacture TAMPAX® (tampon) orCompressed Gel Foam5.

Preferably the buccal cavity stabiliser has a first, ventral face insubstantially the same plane as the plane of the open face of thelaryngeal cuff and the first face of the buccal cavity stabiliser issubstantially concave in shape. This assists the operator with insertingthe device into the patient and with bringing the buccal cavitystabiliser into contact with the patient's tongue.

Preferably the buccal cavity stabiliser extends from the proximal end ofthe laryngeal cuff towards the proximal end of the airway tube such thatthe cuff and the buccal cavity stabiliser are of integral construction.This provides a smooth, elegant device with an appealing and practicaldesign.

Preferably the buccal cavity stabiliser is non-uniform in its width W,having a wide point located at a point intermediate the laryngeal cuffand the proximal end of the airway tube, and more preferably the widepoint of the buccal cavity stabiliser is closer to the laryngeal cuffthan to the proximal end of the airway tube. This arrangement places thewidest or broadest region of the stabiliser in contact with the base ofthe patient's tongue when in use.

Preferably the ratio of the width W of the buccal cavity stabiliser atits widest point to the height H of the buccal cavity stabiliser at thatsame point is 2.7±10%.

Advantageously the face of the buccal cavity stabiliser which comes intocontact with the patient's tongue may be roughened to increase frictionof the stabiliser with the tongue in use.

In a further alternative embodiment the buccal cavity stabiliser isadjustable in size, for example wherein the buccal cavity stabiliser isformed from a unit, at least part of which is slidably mounted withrespect to the airway tube.

In a particularly preferred embodiment the buccal cavity stabiliser isformed as an integral part of the airway tube, and further preferablythe buccal cavity stabiliser, the airway tube and the laryngeal cuff areall formed as an integral unit.

The Shore hardness of the various, parts, portions or components is animportant feature of the invention. For example, the laryngeal cuff ispreferably formed from a material with a Shore hardness on the A scaleof 40 or less and more preferably between 0 to 20, and most preferablybetween 4 to 12.

Preferably the laryngeal cuff and a front, ventral part of the buccalcavity stabiliser are formed from a material of substantially the sameShore hardness. This simplifies construction and ensures that allportions of the device that come into firm contact with the patient'ssoft tissue are relatively soft.

In a further preferred embodiment a back or dorsal part of the deviceand a front or ventral part of the device are formed from materials ofdifferent Shore hardness. This enables the dorsal portion to be made ofa firmer material than the ventral portion.

Preferably the back or dorsal part of the device is formed from amaterial of Shore hardness less than 60 on the A scale, more preferablybetween 25 to 45, and most preferably between 30 to 40.

It should also be appreciated that the laryngeal cuff can be inflatable.Whilst this is not ideal, it still represents a significant improvementover and above prior art inflatable masks.

Preferably the device further incorporates a gastric tube passagewayextending from the lip of the cuff to the proximal end of the device.

According to a second aspect of the present invention there is provideda method of manufacturing an airway device comprising the steps of:—

-   (a) forming mouldings of a first part of the device and a second    part of the device;-   (b) bonding the first part to the second part around a connector.    This represents a considerable simplification over the manufacture    of prior art devices, which are typically multi-component in design.

Preferably the first part is a front, ventral part of the deviceincorporating the face of a laryngeal cuff and the second part is aback, dorsal part in which the first and second parts are formed frommaterials of the same or different Shore hardnesses.

According to a third aspect of the present invention there is provided amethod of manufacturing an airway device comprising an airway tube, alaryngeal cuff and a buccal cavity stabiliser comprising forming thedevice as a one-piece plastics moulding, preferably wherein the deviceis formed by the technique of injection moulding.

It has also unexpectedly been discovered that a stabiliser, whilst stilldesirable, is not essential to achieve a good gas-tight seal between thecuff and the laryngeal inlet of the patient. Since a buccal cavitystabiliser adds both weight and cost there are positive advantages ineliminating this feature from the design. Weight and cost are bothimportant features, particularly where the item is intended as a singleuse or disposable item.

Accordingly, according to a fourth embodiment there is provided anairway device for human or animal use comprising an airway tube having adistal end and a proximal end, the distal end of which is surrounded bya laryngeal cuff, wherein the cuff is non-inflatable and is pre-formedin a shape such that a face region of the cuff is adapted to fit snuglyover the laryngeal inlet of a patient, and wherein the external profileof the tube is substantially uniform between the distal end of the tubewhere it starts to meet the cuff and the proximal end of the tube, andwherein the face region of the cuff is formed from a material with aShore hardness on the A scale of between 0 to 30.

Such an airway device is both efficient in operation and cost-effectiveto manufacture.

Preferably the face region of the cuff is formed from a material ofShore hardness on the A scale of between 0 and 20 and more preferably 0to 5. Preferably the profile of the airway tube is substantiallycircular.

In an alternative embodiment the profile of the airway tube issubstantially elliptical.

Preferably the device further comprises a gastric tube passagewayextending from the distal end of the airway tube to the proximal end ofthe cuff.

Preferably the gastric tube passageway is housed substantially withinthe body of the device.

Preferably the distal end exit of the gastric tube passageway exits thecuff centrally, that is along the line of the central longitudinal axisof the device.

Alternatively the distal end exit of the gastric tube passageway may bedisplaced to one side of the central longitudinal axis of the device.

If the end exit of the gastric tube passageway is displaced it ispreferred that the distal end exit of the device is displaced to theright of the central longitudinal axis of the cuff, as viewed from theopen face of the cuff, in other words to the right-hand side of thepatient when the device is in use. This is for ease of manufacture.

In a particularly preferred embodiment the device further comprises oneor more flexible flanges extending around the opening in the face regionof the cuff.

Preferably the flexible flanges extend substantially around the entirecircumference of the opening in the cuff.

Preferably a plurality of flanges are provided said flanges being spacedapart radially around the opening one from another such that the flangesare substantially concentric.

Advantageously said device further comprises a connector adapted toconnect the proximal end of the airway tube to a gas supply.

Preferably said connector extends into said airway tube and at leastpart way along the length of said airway tube to act as a bite protectorto prevent a patient from constricting the airway tube by biting on it.

Preferably said connector fits into an internal annular recess at theproximal end of the airway tube such that the diameter, or internalcross-section of the airway tube where the tube is non-circularinternally, remains substantially constant along the length of the tubewhen the connector is in place.

Preferably the distal end of the connector abuts in use a shoulder inthe airway tube to prevent the connector from passing into the airwaytube beyond a certain point. This provides a positive fit for theconnector which seats on a shoulder or recess within the tube, andresults in lower resistance to airflow through the device.

Preferably the face of the laryngeal cuff is adapted to form ananatomical fit over the laryngeal inlet of a patient incorporatesprotuberances designed to form a good seal with the pyriform fossae andaryepiglottic folds of the laryngeal inlet of the patient.

Preferably the face of the laryngeal cuff adapted to form an anatomicalfit over the laryngeal inlet of a patient incorporates protuberancesdesigned to form a good seal with the valleculae, epiglottis,aryepiglottic folds, pyriform fossae and around the anterior aspect ofthyroid & cricoid cartilages. The distal tip of the device positionsitself into the recess created by the posterior aspect of the lowerlarynx below the posterior cartilages, above the opening of theoesophagus, not only to help create an airway seal but also to act as aphysical wedge to prevent the possibility of regurgitation.

Preferably the face of the laryngeal cuff adapted to fit anatomicallyover the laryngeal framework of a patient incorporates grooves designedto allow passage of vital arteries, veins and nerves supplying thelaryngeal framework.

Preferably the distal tip of the laryngeal cup is so sized and shaped asto remain above the upper oesophageal sphincter in use.

Preferably the distal tip of the laryngeal cup is substantially concavein shape.

Preferably the face of the laryngeal cuff and the airway tube are formedfrom materials of different Shore hardness.

In an alternative embodiment the face of the laryngeal cuff and theairway tube are formed from material of substantially the same Shorehardness.

Preferably the airway tube together with the back or dorsal part of thecuff are made from material of one Shore hardness and the face of thecuff is made from a material of a different Shore hardness, such thatthe face of the cuff is made of a softer material than the airway tubeand the back or dorsal part of the cuff.

According to a further aspect of the invention there is provided amethod of manufacturing an airway device suitable for human or animaluse, said airway device comprising an airway tube having a distal endand a proximal end, the distal end of which is surrounded by anon-inflatable laryngeal cuff, said method comprising the steps of:

-   (i) providing a mould, the mould including interior walls defining    an interior volume which defines the shape of the airway device;-   (ii) introducing a liquid plastics material into the hollow interior    volume of the mould;-   (iii) optionally introducing a second liquid plastics material into    said mould where it is required that the airway device is made from    materials of different Shore hardness;-   (iv) allowing the plastics material to solidify;-   (v) removing the airway device from the mould.

Preferably said method also comprises the step of inserting into saidmould a connector suitable for connecting to an anaesthetic gas supply,such that, after the moulding process is complete, the connector becomesattached to the airway device.

According to a further aspect of the invention there is provided amethod of manufacturing an airway device suitable for human or animaluse, said airway device comprising an airway tube having, a distal endand a proximal end, the distal end of which is surrounded by anon-inflatable laryngeal cuff, said method comprising the steps of:—

-   (i) providing an airway tube;-   (ii) providing a mould, said mould including interior walls defining    an interior volume which defines the shape of a laryngeal cuff;-   (iii) inserting said airway tube into said mould;-   (iv) introducing a liquid plastics material into the hollow interior    volume of the mould;-   (v) optionally introducing a second liquid plastics material into    said mould where it is required that the cuff of the airway device    is made from materials of different Shore hardness;-   (vi) allowing the plastics material to solidify;-   (vii) removing the airway device from the mould.

Preferably said airway tube is formed by an extrusion process.

In a still further aspect of the present invention there is providedmethod of manufacturing an airway device suitable for human or animaluse, said airway device comprising an airway tube having a distal endand a proximal end, the distal end of which is surrounded by anon-inflatable laryngeal cuff, said method comprising the steps of:—

-   (i) providing a mould, the mould including interior walls defining    an interior volume which defines the shape of a laryngeal cuff;-   (ii) introducing a liquid plastics material into the hollow interior    volume of the mould;-   (iii) optionally introducing a second liquid plastics material where    it is required that the airway device is made from materials of    different Shore hardness;-   (iv) allowing the plastics material to solidify;-   (v) removing the airway device from the mould;-   (vi) providing an airway tube;-   (vii) bonded said airway tube to said laryngeal cuff.

In a still further aspect of the invention there is provided a method ofmanufacturing an airway device suitable for human or animal use, saidairway device comprising an airway tube having a distal end and aproximal end, the distal end of which is surrounded by a non-inflatablelaryngeal cuff, said method comprising the steps of:—

-   (i) providing an airway tube;-   (ii) providing a mould, said mould including interior walls defining    an interior volume which defines the shape of a laryngeal cuff and    which substantially encapsulates the airway tube;-   (iii) inserting said airway tube into said mould;-   (iv) introducing a liquid plastics material into the hollow interior    volume of the mould, to form the back of the cuff and substantially    cover the rigid airway tube-   (v) optionally introducing a second liquid plastics material into    said mould where it is required that the cuff of the airway device    is made from materials of different Shore hardness;-   (vi) allowing the plastics material to solidify;-   (vii) removing the airway device from the mould.

Preferably said airway tube is formed by an extrusion process.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings in which:—

FIGS. 1A to C illustrate various views of the laryngeal cartilages andligaments. This illustration is derived from Tortora G. J., Grabowski G,Reynolds S. Principles of Anatomy and Physiology. John Wiley, 10th Ed,2003. Pg 781, the text and illustrations of which are herein imported byreference;

FIGS. 2 and 3 illustrate in plan view two embodiments of the presentinvention;

FIGS. 4 to 7 illustrate two further embodiments with exploded viewsshowing each airway device in two halves with an airway tube sandwichedbetween the halves;

FIG. 8 shows an optional feature of a second passageway or tunnelstarting at the lateral aspect of proximal end of NLA and curvingtowards the distal end to give its NLA tube/distal opening a posterioraspect of the NLA tube through the mask to allow passage of anorogastric tube;

FIG. 9 shows a longitudinal slit running substantially the length of themask to accommodate an endotracheal tube used in anticipated orunexpectedly difficult intubations; with or without the use of a bougie,Cook's airway or fibre-optic scope.

FIGS. 10.1 to 10.6 show various plan, side and cross-sectional views ofa further embodiment of the present invention.

FIGS. 11, 12 and 13 show two frontal and one side or lateral view of afurther embodiment according to the present invention in which thebuccal cavity stabiliser is adjustable in size;

FIG. 14 shows diagrammatically an airway device according to the presentinvention engaged over a laryngeal inlet;

FIGS. 15A, B, C and D illustrate a number of perspective, cross-sectionand exploded diagram views of an airway device, showing that the airwaytube itself may stand proud of the main body of the device.

FIGS. 16A to F show front, back, side and end elevational views of afurther preferred embodiment of the present invention;

FIGS. 17A, B, C and D show front and side elevations of particularlypreferred embodiments incorporating thin, flexible flanges around partof the circumference of the laryngeal cuff;

FIGS. 18, 19 and 20 show various diagrammatic cross-sectional andisometric views of devices according to the present invention in situ ina human patient;

FIG. 21 illustrates a section along the line Y-Y shown in FIG. 20;

FIGS. 22A, B and C illustrate front, side and rear elevational views ofan airway device according to a first embodiment of the presentinvention having a substantially circular profile airway tube;

FIGS. 23A to D illustrate various perspective views of the embodimentshown in FIG. 23;

FIGS. 24 A, B and C show front, side and rear elevational views of anairway device according to a second embodiment of the present inventionhaving a substantially elliptical profile airway tube;

FIGS. 25A to D illustrate various perspective views of the embodimentshown in FIG. 25;

FIGS. 26A to D illustrate various perspective views of an embodimentwithout a gastric tube passageway;

FIGS. 27A, B and C illustrate front, side and rear elevational views ofan airway device according to a further embodiment of the presentinvention;

FIGS. 28A to D illustrate perspective views of the embodiment shown inFIG. 27;

FIGS. 29A, B and C show enlarged rear, side and front elevational viewsof a laryngeal cuff; and

FIG. 30 shows an enlargement of a cuff, detailing the split line betweendifferent plastics which would be present if the cuff is to be formed bymaterials of two different shore hardnesses;

FIGS. 31A to D illustrate a connector which can also act as a biteprotector;

FIG. 32 illustrates a front elevational view of a laryngeal cuff inwhich the gastric tube passageway exits on the mid-line or centrallyfrom the tip of the cuff;

FIGS. 33 to 39 show front, back, side and end elevational views of afurther embodiment of the present invention;

FIGS. 40 to 49 show front, back, side and end elevational views ofanother further embodiment of the present invention;

FIGS. 50 to 56 show front, back, side and end elevational views ofanother further embodiment of the present invention;

FIGS. 57 to 63 show front, back, side and end elevational views ofanother further embodiment of the present invention;

FIGS. 64 to 70 show front, back, side and end elevational views ofanother further embodiment of the present invention; and

FIGS. 71 to 77 show front, back, side and end elevational views ofanother further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below by way ofexample only. These examples represent the best ways of putting theinvention into practice that are currently known to the applicantalthough they are not the only ways in which this could be achieved.

Referring to FIG. 2, this illustrates the distal end of a mask deviceaccording to a first embodiment of the present invention, generallyshown as 10. This comprises an airway tube 11, which at its proximal end12 (not shown) terminates in a 15 mm or other connector suitable forconnection to an anaesthetic breathing system of conventional type.Formed around the distal end 13 of the airway tube is a laryngeal cuffor cup 14 adapted in its shape and contours to correspond with thelarynx inlet region of a patient. In this context the terms cuff and cuphave an equivalent meaning. They refer to the element of the device atthe distal end of the airway tube that is adapted to cover and form aseal with the laryngeal inlet of the patient. In the context of thisdescription, the term proximal means the end of the device, or portionthereof, closest to the connection to the anaesthetic breathing system.The term “distal” means the end of the device, or portion thereof,furthest from the anaesthetic breathing system.

Laryngeal cuffs, in general, are well known to the specialist and theanatomy of the laryngeal inlet region of a human are shown in somedetail in FIGS. 1A, B and C. The particular cuff shown in FIG. 2incorporates in the cuff face pronounced and discernable bulges orprotruberances 15, 16 designed to form a good seal with the piriformfossae and aryepiglottic folds. It will be appreciated that theoutbulgings in the cuff at 15 and 16 are positioned antero-laterally togive an anatomical seal by fitting into the piriform fossae andaryetriglottic folds. Thus, in side elevation, the face of the cuff isnot a flat planar surface but includes regions that protrude above thegeneral plane of the cuff face. Additionally, there may optionally beregions which lie below the general plane of the cuff face. Theseshapings and the general size, shape and configuration of the surface ofthe cuff face around opening 17 are an important feature of theinvention. Alternative shapes for the face of the cuff are shown inFIGS. 3, 5, 10, 11, 12, 17 and 18 and are described in more detailbelow.

The device may be constructed from any suitable plastics material asselected by the materials specialist. Latex-free medical grade siliconerubber is one preferred material. The cuff should be soft in texture toavoid undue damage to the surrounding tissue. Other suitable materialsfor construction of this type of device include, but are not limited to,Poly Vinyl Chloride (PVC), Thermoplastic Elastomers such as the styrenicblock copolymers (eg Styrene Butadiene Styrene (SBS), Styrene EthyleneButylene Styrene (SEBS)), and Thermoplastic Olefin Blends (TPO),Thermoplastic PolyUrethanes (TPU), Copolyester (COPE), Polyether BlockAmides (PEBAX) and foamed versions thereof, where appropriate.

A further important factor involved in the choice of a suitable materialis transparency. Ideally the material or materials of constructionshould be substantially clear or transparent. This enables theanaesthetist or operator to see the inner lumen of the airway to checkfor blockages or other problems. Such transparent materials are known tothe materials specialist.

In one preferred embodiment the cuff is non-inflatable and is formedfrom any suitable soft plastics material. By way of a preferred softness(hardness) range, on the Shore A scale of Hardness, a hardness of lessthan 40 for the face of the cuff that contacts the laryngeal inlet isoptimum. By way of a preferred range, a value on the same scale ofbetween 0 to 20 is preferred, with a particularly preferred range of 4to 12. The softness of the cuff can be further adapted by formingcavities or channels within the body of the cuff itself (shown in FIGS.4 and 5).

In a further preferred embodiment the cuff may be pre-filled with afluid such as air, or other non-toxic gas, or a non-toxic liquid. Inthis context the term fluid has a broad meaning and includes anysuitable gas, liquid, vapour or combination thereof and will bedetermined and designed by an expert in this field ofanatomy/anaesthesia in conjunction with the materials specialist. Thecuff will be constructed of such a material which will not allow nitrousoxide (anaesthetic gas) to diffuse through the material to anysignificant amount so that the extra luminal pressure is kept constant.It follows therefore that the cuff should be substantially impermeableto the fluid with which is filled and to anaesthetic gases.

Alternatively, the cuff can be formed from a soft, foamed material orcan be foam filled. In either case this provides a soft deformable butshaped surface around the face of the cuff to engage over the anatomy ofthe larynx inlet region. Such a foam filled device will minimise anypotential damage to the structures in that region whilst still providinga substantially complete seal.

Directly adjacent to the laryngeal cuff/cup but positioned on theproximal side of the airway tube to the cuff itself is a buccal cavitystabiliser 20. In this example this stabiliser takes the form of anexpanded region extending symmetrically on either side of the airwaytube. This stabiliser is adapted to rest on the anterior aspect or frontof the tongue and is configured to correspond with the anatomy of thatpart of the patient.

A wide variety of shapes, sizes, and positions for this stabiliser arepossible. The one illustrated in FIG. 2 is curved in the plane of thecuff face such that the face visible in FIG. 2 is slightly concave, withthe rear face being slightly convex. The face of the stabiliser may beroughened, scored or serrated to increase the friction with the tongueand thus stabilise it in use, to avoid or reduce forward or backwardsmovements when in use.

In this example the stabiliser is formed integrally with the cuff, suchthat one runs smoothly into the other. However, this is not essentialand the stabiliser could be a separate unit on the airway tube. Anessential feature of the stabiliser is that it is broader incross-section than the diameter of the airway tube itself. That is tosay it extends into a region either side of the airway tube and in thesame generally plane as the laryngeal cuff. Preferred dimensions for thebuccal cavity stabiliser will be discussed below.

A further example of a different design of buccal cavity stabiliser isillustrated in FIG. 11, 12 and 13. In this example the stabiliser 50 isadjustable and has two side hooks 51, 52 at the lateral aspects, nearthe proximal end of the airway tube, which can be slid downwards andupwards to increase or decrease the size of the flanges for adequatestability, and for the ease of insertion and removal of the NLA. Thehooks engage into ratchet strips 53, 54, formed in opposing sides of theairway tube. The stabiliser is formed from a resiliently deformable,flexible material such that as the hooks are forced from their positionas shown in FIG. 11 to a position closer to the cuff at the distal endof the tube, as illustrated in FIG. 12, the spread of the stabiliser oneither side of the airway tube increases the more the hooks are movedtowards the cuff, and therefore the broader the stabiliser. Thus thestabiliser extends from the proximal end of the airway tube, just belowthe connector to the proximal end of laryngeal cuff. The stabiliser issubstantially symmetrical in shape and can be slid down to give anexpanded shape across the buccal cavity. FIG. 13 shows an obliquelateral view of this embodiment.

This is just one of the many methods which could be used to form astabiliser. A stabiliser could be formed from any, preferably soft,extension around the airway tube wall that can lie on the anterioraspect of the tongue. Any suitably shaped laterally extending flangewhose body lies mainly along the longitudinal axis of the airway tubewould serve this purpose. The flange need not be solid, so a tubular,mesh or other perforated structure would be perfectly acceptable. Thestabiliser preferably has a concave face or region when viewed from thedirection shown in FIG. 11, ie from a direction normal to the face ofthe cuff, that conforms substantially to the anterior region of thetongue of the patient.

It is also possible to form such a “flange” by broadening the profile ofthe airway tube at the appropriate region, just above the cuff. That isto say, the buccal cavity stabiliser may be an integral part of theairway tube, rather than being a separate component formed on or aroundthe airway tube itself. Thus, a suitable increase in the general profileof the airway tube, whether formed by the tube itself or by formingadditional material around the tube, can act as a stabiliser.

The general profile of the buccal cavity stabiliser and the way that itmerges smoothly into the cuff region can be seen in more detail fromFIGS. 16 and 17A and B, which will be described in more detail below.However, it will be appreciated that both weight and plastics materialwould be saved if the internal diameter or profile of the airway tubeincreased and decreased correspondingly with the width of the buccalcavity stabiliser. The term “internal profile” is used because, as theairway tube broadens it becomes non-circular and instead assumes asubstantially elliptical shape. It will therefore be appreciated that inthis embodiment the cross-sectional area of the airway tube increases asthe width of the buccal cavity stabiliser increase to its widest pointand then decreases again. By maximising the width of the airway tubethis has the potential to increase laminar flow within the device.

A further feature of the airway device shown in FIG. 11 are the two setsof protrusions or bulges 56, 57 and 58, 59 on the face of the cuff. Thelarger of the two sets 56, 57 are adapted to around the aryepiglotticfolds and in the pyriform fossae. The smaller of the two 58, 59 areadapted to fit around the Thyroid and Cricoid cartilages. In addition,the tip of the cuff 55 is a soft, tapered lip but is preferably notinflated.

A further example is illustrated in FIG. 3. This illustrates an airwaydevice 30 having a cuff 34 and a buccal cavity stabiliser 40. In thiscase there are two outbulgings or protrusions on either side of the cuff35, 36, 38 and 39. An upper set, 38, 39 consisting of one protrusion oneach side, is designed to lie around the aryepiglottic folds and in thepyriform fossae. The lower set 35, 36 are designed to lie around thethyroid and cricoid cartilages. The relative sizes of these bulges willbe determined by the appropriate specialist. It is probable that thebulges 38 and 39, designed to fit around the aryepiglottic folds and inthe pyriform fossae will be slightly larger than the two lower bulges.The distal/lower end of the cuff is soft but firm, and preferably notpre-inflated or pre-filled for the ease of the device's insertion, andadapted to lie in between the larynx and oesophagus. Further variationsare shown in FIGS. 4 to 7, which show the flexibility possible withinthis general design concept. FIGS. 6 and 7 illustrate the possibility ofincluding an additional moulding 60 on the proximal end of the unit.

FIG. 5 illustrates one possible method of manufacture of a deviceaccording to the present invention. The device is manufactured fromappropriate material as described previously in two halves 81 and 82.The two halves are bonded together around an airway tube 83 (not shownfor clarity). The airway tube fits into a specially designed channel 84.In this example the buccal cavity stabiliser 90 is moulded integrallywith the cuff 94. The tip of the device contains a series or pluralityof cavities 91, 92 and 93. In this context plurality means one or more.These cavities increase the flexibility of the tip, which aids theinsertion, and positioning of the device in use. These cavities alsoaffect the softness and pliability of the tip, their presence making thetip softer than if it was formed from solid plastics material.Generally, the softer the material, the less potential there is todamage the tissue of the patient. The generally concave nature of thedevice is also apparent from FIGS. 4 and 5.

A further feature in these embodiments which is apparent from thesefigures is that the distal tip of the device tapers to a gentle point.This tapered end is intended to lie or wedge between the larynx and theoesophageal inlet.

An understanding of one method of constructing an airway deviceaccording to the present invention can be appreciated from FIGS. 4 to 7inclusive. Basically, the device in FIG. 7 is formed in two parts 61 and62 plus a moulding 64 which includes a 15 mm or other connector toconnect the device to an anaesthetic breathing system. 61 is a ventralor front moulding, being that portion which comes into contact with thepatient's laryngeal inlet and tongue. 62 is a dorsal or back moulding,being that side which faces away from the ventral portion. Thesedefinitions of ventral and dorsal are used throughout thisspecification.

Optionally the device may also include a separate airway tube 63 thatnests within channels 66, 67 formed within the internal body ofmouldings 62 and 61 respectively. However, in a particularly preferredembodiment this separate tube 63 is omitted. In this example the tube 63and mouldings 62 and 61 are made of silicone rubber and the mouldings 64and 68 from polypropylene. The larger of the two polypropylene mouldings68 is designed to prevent the device passing into the patient's mouthbeyond a certain point.

The airway tube may be of any appropriate diameter, or cross-section ifthe tube is not circular. Typically a 9 mm tube would be used in anadult version of the airway device.

The mouldings 61 and 62 are bonded, glued, welded (including but notlimited to heat welding and laser welding) or otherwise fixed togetherduring assembly. It follows from this simple, elegant and cost-effectiveform of manufacture that the two components 61 and 62 can be formed frommaterials with different hardnesses. Thus the front portion of 61 thatcontains the laryngeal cuff can be made out of a softer material thanthe back portion. Typical Shore hardnesses on the A scale for the frontportion 61 are between 0 to 20, more preferably 0 to 15 and morepreferably 4 to 12.

The rear portion 62 has typical Shore hardness values of 20 to 60 andmore preferably 30 to 40.

It is possible to incorporate an additional passageway 70 or passagewayswithin the body of the unit and alongside the airway tube. An example ofthis is illustrated in FIG. 8. This passageway allows other tube(s) orwire(s) to be passed down the oesophagus during use without the need tomove or disturb the device. For example, orogastric intubation nowbecomes possible.

In another variant, shown in FIG. 9, the airway incorporates alongitudinal slit extending substantially the whole length of thepassageway. This allows other tubes or wires (bougies, stylets etc) tobe inserted or withdrawn during use without the need to disturb themask, during planned or unexpected difficult intubations. Furthermore,this slit arrangement means that the airway device can be released fromthe tube or wire and removed from the patient leaving the tube or wirein place undisturbed.

FIG. 10 shows a further embodiment of the present invention and alsoshows the generally curvilinear shape of the device along itslongitudinal axis. This shape is designed to correspond with themouth/throat opening in an anaesthetised patient. The longitudinal axisis the axis line shown as the straight dotted line in FIG. 10.4 and runsfrom the proximal and of the airway tube to the distal tip of the cuff.

The general shape of one preferred embodiment of the buccal cavitystabiliser is shown in FIG. 10.3. The stabiliser, generally shown as100, is formed around an airway tube 101. However, as described above, aseparate tube is not necessary and a tubular passageway can be formedfrom channel(s) formed into the body of the stabiliser. The stabiliserportion extends 102, 103 on both sides of the tube 101 in a generallyelliptical cross-section. It will be appreciated from FIG. 10.1 and 10.5and FIGS. 17 and 18 that the width of the buccal cavity stabiliser isnon-uniform and varies along its length. This is in contrast to theairway tubes of similar prior art devices, which are generally uniformin cross-section. The width in this context is the edge-to-edgedimension in a direction normal to the longitudinal axis of the deviceand in a plane substantially parallel to the plane of the open face ofthe cuff. The stabiliser is narrowest at the proximal end of the device,then increases in width to a widest point, and then decreases in widthagain until it merges into the proximal side of the laryngeal cuff. Thewidest point of the stabiliser is therefore between the proximal end ofthe airway tube and the proximal end of the laryngeal mask. Generally itis advantageous if the widest part is nearer to the laryngeal mask endthan it is to the proximal end, as shown in FIGS. 17A and B. Thislocates the widest part nearest to the anterior region of the patient'stongue in use.

Importantly the height H of the stabiliser does not vary in a similarway. Rather the height remains substantially the same along thelongitudinal axis of the stabiliser. This is quite different fromconventional airway tubes.

It will be evident from the foregoing that the width of the ellipse W atits widest point is greater than the height H at the same point. By wayof example, for an adult airway device according to the presentinvention the width W of the stabiliser, at its widest point, would bein the range 3.5 cm to 4.5 cm and the height H would be in the range1.25 cm to 1.75 cm. A preferred ratio of W:H is 2.7±10%.

An important feature of the shape of this stabiliser is the profile ofthe upper 104 and lower 105 outer surfaces. These are both convex andgently curved in their broadest regions. This not only makes for ease ofuse but, more importantly, the lower surface 105 which comes intocontact with the tongue in use, is profiled to follow the shape of theback of the patient's tongue and is soft enough to deform to conform toit.

A further embodiment is illustrated in FIG. 16. In this embodiment theairway tubing 111 is only partly contained within the body of the airwaydevice 110. The distal end of the tube passes into and completelythrough the body of the device to form an opening within the cuff 113.In this embodiment a different profile of stabiliser is illustrated. Inthis case the lower surface 115, which contacts the tongue in use, isgently concave in shape, with the upper surface being generally convex.

Once bonded together, the device becomes what is, in effect, a unitaryconstruction. That is to say, the components become as one. Thissimplifies sterilization, if the devise is reusable, and increasesreliability.

However, unitary construction is not essential. For example, it may bepossible to form the buccal cavity stabiliser as a separate component(not shown) that is threaded over, around or on to the airway tube ifrequired. This design would give the anaesthetist the option of usingthe device with or without a stabiliser as desired. It would benecessary to incorporate some form of securing means to secure thestabiliser to either the cuff or the tube. Means of fixing or securingplastic components are well know, such as snap-fit connectors.

This option increases the design options for the stabiliser. A form ofleaf spring, secured at one or both ends to the airway tube could beemployed. Alternatively an inflatable structure could be used. It willbe recalled that inflatable cuffs have been used in this context.However, this type of technology has never been used before toincorporate a buccal cavity stabiliser into a device of this type.

Two further embodiments are illustrated in FIGS. 17 and 18. Theseillustrate the streamlined, unitary construction of these embodiments ofthe invention, with the cuff region 121 merging smoothly into the buccalcavity stabiliser region 122. There are certain other key features shownin these Figures. For example, where the airway tube enters thelaryngeal cuff, it does so through three separate apertures 123, 124 and125. This greatly decreases the chance of the airway tube being blocked.The shape of the distal end of the stabiliser joining the proximal endof the cuff/cup is designed in such a way that when the device is insitu, it fits anatomically correctly in and around the valecullae.

The distal tip of the cuff 126 has been truncated and in fact is nowconcave in shape. This results in less compressive pressures beingexerted over the thyroid and cricoid cartilages, blood vessels andnerves supplying the laryngeal framework than is the case with prior artdevices. This so-called concave tip can take a variety of differentshapes and forms. The tip may be “squared off” such that the end of thetip is substantially planar. Or there may be a pronounced indentation inthe tip, as shown in FIG. 17A. At the base of that indentation is anaperture forming the end of a gastric tube passageway described below.In summary, this truncation is intended to encompass any tip whichresults in less compressive pressure being exerted than by prior artdevices.

A second, gastric tube passageway, separate to the airway tube isprovided which runs from an opening 127 in the proximal end of thedevice near the connector 128 to an opening in the distal tip of thecuff 129, more clearly shown in FIG. 17E. The gastric tube allows forany gastric aspirate to be detected in the event of passiveregurgitation during use. It also provides a route for the insertion ofsmall-bore gastric tubes (eg Freka Tubes).

A further novel feature of this device is the lip or flange 130 locatedat the proximal end of the cuff region. This lip is sized and shaped soas to be anatomically positioned against the epiglottis, to ensure aproper seal and to hold the epiglottis back from folding towards thelaryngeal inlet avoiding obstruction to airflow. This tip takes the formof a leaf like structure extending out of the laryngeal cuff anddirected back towards the proximal end of the airway tube. Its relativesize and shape can be seen from FIG. 17. The optimum size and shape willbe determined by experimentation. The applicant is not aware of anyprior art masks which contain this feature.

FIG. 18 also illustrates certain novel features of construction and ofthe laryngeal cuff. Turning first to the cuff, in this embodiment thin,flexible featherlike flanges 140 and 141 have been introduced onopposing sides of the cuff. These are preferably formed as an integralpart of the moulding of the cuff and, because of the very soft nature ofthe material used to form the cuff, these flanges are particularly softand pliable. Their purpose is to make allowance for any individualpatient variation in the laryngeal inlet shape and to contribute toforming an efficient and effective seal between the cuff and thelaryngeal structures. By this design, and by designing the cuff to be aclose anatomical fit, the obtainable seal pressure from experimentaltrials is well in excess of 30 cm H₂O.

The feather-like flanges 140 and 141 are shown in FIG. 18 asdiscontinuous structures but these can in fact be connected to eachother towards the distal end of the cuff (FIGS. 18C and D). In thisarrangement flanges 140 and 141 become a single U-shaped flangeextending around the majority of the laryngeal cuff perimeter.

Also shown in FIG. 18 is a two-part form of construction. The two partsare an upper, curved portion 145, whose outer surface is generallyconvex and a lower curved portion 146 whose outer surface is generallyconcave and which includes the face of the laryngeal cuff which contactsthe patient's laryngeal inlet in use. Formed within these two portionsis an airway tube channel that extends from the proximal end 147 to thedistal or cuff end 149, and the second passageway described above.

The upper and lower parts are then bonded together around connector 150by use of a suitable adhesive or welding technique as selected by thematerials specialist.

The upper portion 145 and the lower portion can advantageously be formedfrom materials having different Shore hardnesses. Thus, the upperportion can be formed of a material having a Shore hardness on the Ascale in the range of 30 to 40, whereas the lower portion can be formedfrom a softer material with a hardness in the range 4 to 12 on the samescale.

If required, the cuff region can be formed from a different material andof a different hardness, from other parts of the device. Thisarrangement is shown in FIG. 17C where the device is formed in threeparts 135, 136 and 137 rather than two.

However, the elegant and simple design of this airway device does allowfor an even simpler method of manufacture. It has been discovered thatthe device can be moulded as a one-piece unitary construction in onemould. By constructing the mould appropriately, and by carefulconsideration of how the mould parts separate, one-piece manufacture ispossible. The moulding may be produced using a process commonly known as2 shot injection moulding, in which the materials are injectedseparately to form the relevant parts of the component. Alternatively,the component could be formed from material of the same hardnessthroughout using a single injection process, and if desirable overlain,in all or part of the ventral or dorsal section, with a material ofdiffering Shore hardness. The technology for forming such overlay orlaminates is known to those skilled in art.

Turning now to the design of the laryngeal cuff, in the foregoingexamples the cuff region has been pre-formed from a soft material, orpre-filled during manufacture with a fluid. In the latter case thelining of the cuff should be made from a material that does not absorbanaesthetic gases such as Nitrous Oxide, such that the pressure insidethe cuff does not rise during use.

In any alternative embodiment the cuff may be formed from a materialwhich is adapted to absorb a liquid, such as water, mucous or blood orsimilar liquid material and in doing so to swell in size so as toconfirm to the anatomical mucocartilagenous framework of the patient'slaryngeal inlet. Such materials will be selected by the materialsspecialist but include CRM (cotton rayon mixes) as used in TAMPAX®tampons, or compressed Gel Foam 5.

In a further, alternative embodiment, the cuff could take the form of aconventional, inflatable cuff. Whilst this is not ideal, because of theinherent disadvantages of inflatable cuffs, the incorporation of abuccal cavity stabiliser of the type described above, made from softmaterials as described above, into an inflatable laryngeal mask airwaydevice represents a significant improvement over and above prior artinflatable masks. The technology to form an inflatable cuff is wellknown and need not be described here.

In summary, the aims and objectives of the present invention are toprovide an anatomically oriented, versatile, reliable, simple and costeffective device intended to be used in spontaneously breathinganaestetized patients or patients recovering from anaesthetic, incertain group of intensive care patients during their weaning processand during resuscitation, to provide a secure, clear and hands-freeairway for the delivery of oxygen and/or anaesthetic gases.

Main aims and objectives are as follows:—

-   -   To provide a simplified design which has all the advantages of        existing airway devices and has an anatomically oriented working        mechanics in order to establish a clear airway in spontaneously        breathing anaesthetized patients, patients in post-anaesthetic        recovery phase or certain group of intensive care patients        undergoing weaning off their ventilatory support.    -   Avoids almost all the disadvantages and complications of        currently used airway devices in anaesthetic practice.

No need of laryngoscopy, intubation, or extubation and minimallyinvasive to pharyngo-larynx.

-   -   User friendly, would require minimal training for anaesthetists,        other doctors, nurses, paramedics and rest of the health care        staff likely to use the device.    -   A useful tool in the management of an unexpected or/and        anticipated difficult endotracheal intubation. Useful either        with an endotracheal tube through the airway or with planned        Fibre-optic intubation or bronchoscopy.    -   Self-retaining with hardly any need to tape or tie.

In summary the device has a Connector, expanded glosso-pharyngealflanges and a pre-formed, pre-inflated or pre-filled anatomicallydesigned laryngeal cup or cuff suited to the exact contour and shape ofthe laryngeal inlet. However, this should not be seen to prevent thisinvention being used with a conventional, inflatable cuff.

Connector:

15 mm ISO standard connector suitable to be connected with any of thegas delivery systems used in anaesthetic, during post-anaestheticrecovery, in intensive care and resuscitation practice.

Expanded Glosso-Pharyngeal/Buccal Flanges:

All the existing airways intubation devices have a varying degree ofpropensity to lateralize towards right or left angle of the mouth,rotation through 180 degrees about it's longitudinal axis and themovements of the airway inwards or outwards, which can lead to thedisplacement or misplacement of the distal end of the airway thusbecoming ineffective for the purpose of it's use. A combination of theexpanded flanges of the device, and constructing the device from amaterial of a Shore hardness less than 60 on the A scale, enables thebuccal cavity stabiliser to act as an anchor for the airway device inthe midline position by stretching over the anterior surface of thetongue across the buccal cavity and supported laterally by inner surfaceare aimed for better anchorage of the airway over the tongue. Thus, notonly stabilizing the airway device positioned centrally but alsostopping it to lateralize and/or rotate. Distally the expanded flange isincorporated into the flattened and angular part of the laryngeal cupwith the postero-inferior surface of the tubular part of the devicedistally, in order to provide additional anchorage into the narrowhypopharynx.

Anatomically Oriented Laryngeal Cup:

A soft rubber or pre-formed, pre-inflated/pre-filled with a suitableliquid or soft material cup aimed not to exert an extra-luminal pressureof more than 22 mmHg onto the rnucosa of Laryngeal inlet and adjacentstructures thus avoiding any compression or shearing forces onto thepharyngo-laryngeal mucosa ensuring a continued, uninterrupted blood flowthrough the capillaries of the surrounding tissues, thus ensuring anuninterrupted blood supply of the structures in contact with it.Anatomically oriented laryngeal cup sealingly surrounds the laryngealinlet without distorting the structures with which it is in contact.

Laterally the out-bulgings of the cup or cuff are designed to fit aroundthe pits of the Aryepiglottic folds and infero-laterally piriformfossae. The tapered lower end is for the ease of its passage through theoro-pharynx which will provide a seal over and beyond the interarytenoidfold in the midline and cuneiform and corniculate cartilages laterally.An upper midline slit will help the cup's passage over the epiglottiswithout damaging or folding and twisting the epiglottis into the cavityor distal opening of the device into the cup. Above the slit, is theflatter part of the soft cup which is designed for the optimal placementin the hypo-pharynx in between the epiglottis and the base of the tonguethus separating the surrounding structures away from the glottis.Although the cup provides a near natural and anatomical seal over theglottic opening but still prevention from the aspiration of regurgitatedgastric contents cannot be guaranteed. Such risk could be minimized byusing a modified device with an oesophageal component in high riskpatients.

Sizes:

Sizes from 0-7 are envisaged.

1 to 2 for neonates and infants (weight 3-20 kgs) 3 for children (weight21-50 kgs) 4 to 5 for adolescents (weight 51-90 kgs) 6 to 7 for adults(weight more than 90 kgs)

Re-usable or disposable devices may preferably be made of materials asdescribed above such as latex-free SEBS or medically graded siliconerubber. A re-usable (sterilizable) device would be capable of at least40 uses. The simplicity of the design also offers increased ease ofsterilization for the purpose of its reuse. Disposable devices would bea preferred choice of production which will be not only more economicalbut also devoid of any risk of cross infection as may be the case inre-usable devices.

As a result of the above design features a device according to thepresent invention, is likely to cost much less than any comparabledevice.

NLA with Oseophageal Component

Addition of an oesophageal component is intended to be used in patientswith a suspicion of gastric statis under anaesthetics, in Intensive CareUnits and for the patients with highly irritable airways who pose a wellrecognized and wide spread problem of weaning from ventilatory support.Such patients almost certainly end up with Tracheostomy in order tobypass their upper irritable airway, to facilitate weaning. Patientswith chronic obstructive/restrictive airway disease, asthmatics andheavy smokers are the ones who are more likely to pose the weaningproblem.

Intubating NLA

Morbidity or mortality in patients with an anticipated or/and unexpecteddifficult intubation is a well-recognized aspect of anaesthetic practiceand a challenging nightmare for any anaesthetist when faced with thatsituation. A modified version of the NLA with a preformed longitudinalslit to the anterior of NLA will help facilitate intubation through theNLA with an endotracheal tube with the help of bougie, Cook's airway ora fibre-optic scope.

Others

Some modifications to the shape, design and working mechanics of each ofthe Component of the NLA are envisaged, whether needed for NLA'simproved Performance or aesthetic look.

-   -   The whole of the airway device could be manufactured as a single        unit- or each component of it manufactured separately if it is        deemed necessary for the sake of its improved function or cost        effectiveness or due to any other issue of practicality.

It will be appreciated that, as used herein, the anatomical terms“anterior” and “posterior,” with respect to the human body, refer tolocations nearer to the front of and to the back of the body,respectively, relative to other locations. In the context of thisdescription, the term “proximal” means the end of the device, or portionthereof, closest to the connection to the anaesthetic breathing system.The term “distal” means the end of the device, or portion thereof,furthest from the anaesthetic breathing system or alternatively, thecuff end of the device. The term “lateral” refers to a location to theright or left sides of the body, relative to other locations.“Bilateral” refers to locations both to the left and right of the body,relative to other locations. The anatomical term “medial” or “medially”refers to a location toward the centre or midline of the body, relativeto locations both to the left and right of the body.

The airway devices described above have a soft laryngeal cuff adapted tofit anatomically over and form a seal with the laryngeal structure of apatient. An essential feature of these embodiments of this device is aso-called buccal cavity stabiliser, located around the airway tube, andwhich is designed to nest with the anterior aspect of the patient'stongue.

The laryngeal cuffs on these devices are generally non-inflatable, butrather are formed from a soft, deformable material that can adapt to theindividual detail of the patient's laryngeal inlet to form asatisfactory seal. It was precisely because of the very soft, deformablenature of these cuffs that it was considered necessary to incorporatesome form of stabiliser to locate the cuff during insertion and tomaintain a good gas-tight contact with the laryngeal inlet at all timesduring use. It should be borne in mind that “use” can involve thepatient in many hours on the operating table under anaesthesia and canalso involve use in accident and emergency situations involving hostileconditions that are non-ideal for such treatments.

Referring to FIG. 23, this illustrates front, side and rear elevationsof an airway device according to a first embodiment of a further aspectof the present invention, generally shown as 510. This comprises anairway tube 511, which at its proximal end 512 terminates in a 15 mm orother connector 518 suitable for connection to an anaesthetic breathingsystem of conventional type. Formed around the distal end 513 of theairway tube is a laryngeal cuff or cup 514 adapted in its shape andcontours to correspond with the laryngeal inlet region of a patient. Inthis context the terms cuff and cup have an equivalent meaning. Theyrefer to the element of the device at the distal end of the airway tubethat is adapted to cover and form a seal with the laryngeal inlet of thepatient in use. The anatomy of the laryngeal inlet region of a human iswell known to the expert. It is illustrated in some detail in FIG. 1 andthe key thereto.

The cuff 514 has an opening 517 in a face or front region of the cuffand the back or dorsal part of the cuff is closed. The opening 517 inthe face of the cuff connects directly to the airway tube 511 such thatgas is free to flow from the connector 518 through the airway tube andout of the open face of the cuff.

The particular cuff shown in FIG. 23 incorporates in the cuff facepronounced and discernable bulges or protuberances 515, 516 designed toform a good substantially gas-tight seal with the piriform fossae andaryepiglottic folds. It will be appreciated that the outbulgings in thecuff at 515 and 516 are positioned antero-laterally to the laryngealframework and give an anatomical seal by fitting into the piriformfossae and aryepiglottic folds and space postero-inferior to the thyroidand cricoid cartilages, and the posterior cartilages (corniculate andcuneiform). Thus, in side elevation, the face of the cuff is not a flatplanar surface but includes regions that protrude above the generalplane of the cuff face. Additionally, there may optionally be regionswhich lie below the general plane of the cuff face. These shapings andthe general size, shape and configuration of the surface of the cuffface around opening 517 are an important feature of the invention.

Thin, flexible, featherlike flanges 520 and 521 extend substantiallyaround the circumference of the opening 517 in the face region of thecuff. These flanges are preferably formed as an integral part of themoulding of the cuff and, because of the very soft nature of thematerial used to form the cuff, these flanges are particularly soft andpliable. Their purpose is to make allowance for any individual patientvariation in the laryngeal inlet shape and to contribute to forming anefficient and effective seal between the cuff and the laryngealstructures. By this design, and by designing the cuff to be a closeanatomical fit, the obtainable seal pressure from experimental trials iswell within the range of 12-40 cm H₂O, which is sufficient forventilation.

These flanges need not completely encircle the opening 517 as shown inFIG. 1 but it is preferred that they completely surround the openingcircumference, and in doing so they follow the general contours of thefront face of the cuff. Flanges 520 and 521 are spaced apart slightlysuch that each flange is an integral item or unit. The flanges arespaced radially one from another around the opening such that one flangesurrounds another. The term “radially” in this context has a broadmeaning and refers to the spacing of each flange from an imaginary axisextending out of the opening in a plane substantially perpendicular tothe general plane of the cuff face.

In this embodiment two feather flanges are shown. However, there may beno flanges, one flange or two or more than two flanges. In other wordsthere may be none or a plurality of flanges, “plurality” having themeaning one or more in the context of this disclosure.

A further feature of the cuff is the epiglottic rest 530 located at theproximal end of the cuff region. This epiglottic rest is sized andshaped so as to be anatomically positioned against the epiglottis, toensure a proper seal and to hold the epiglottis back from downfoldingtowards the laryngeal inlet avoiding obstruction to airflow. Thisepiglottic rest takes the form of a leaf like structure extending out ofthe laryngeal cuff and directed back towards the proximal end of theairway tube. Its relative size and shape can be seen from 530A in FIG.31. The optimum size and shape for this epiglottic rest will bedetermined by experimentation.

Turning now to the airway tube, this is shown generally as 511 in FIG.23. This tube, which is in the form of a hollow cylinder ofsubstantially uniform cross-section open at each end, extends from theconnector end 512 into the body of cuff 514 to connect with cuff opening517. The inside diameter of the airway tube will depend on the size ofthe device, generally larger in adult sizes versus paediatric sizes, anddesigned in general to accommodate the appropriately sized endotrachealtube for endoscope guided intubation where necessary. The internaldiameter of the tube may be substantially uniform along its length,although the internal diameter may vary.

In terms of intubation the airway device also has significant benefitsover inflatable laryngeal cuffs during retrograde intubation procedures.This is because inflatable cuffs can potentially be punctured anddeflated, which could result in lack of seal and problems withventilation.

The tube is formed from a bendable plastics material that will bedescribed in more detail below. With the exception of the region at thedistal end of the tube where it starts to join the cuff, the externalprofile of the tube is substantially uniform between the distal end ofthe tube where it starts to meet the cuff and the proximal end of thetube. The term “substantially uniform” means that there is no region ofthe tube which could act as a buccal cavity stabiliser ie an expandedregion extending on either side of the airway tube. Put another way,there is no section of the tube that extends on either side of the tubeand which is generally broader in profile than the airway tube itself.The internal diameter of the airway tube will preferably besubstantially uniform and circular, whether the tube has a circular oroval exterior profile, and the distal opening of the airway tube intothe cuff is a single opening to help reduce the resistance to flowthrough the device.

The airway tube can be formed with a variety of profiles. In theembodiment illustrated in FIGS. 23 and 24 the general external profileof the airway tube is substantially circular. This can be seen mostclearly in FIG. 24D. In contrast, in the embodiment illustrated in FIGS.25 and 26, the airway tube has a generally elliptical external profile,although the bore passing through the airway tube is substantiallycircular in cross-section. These are just two of many profiles thatmight be selected by the designer.

A connector 618 which fits into the end of the airway tube is shown inmore detail in FIG. 32. There are two important features to note fromthis embodiment. Firstly, the length of the connector is significantlygreater than a conventional connector and is such that it extends, inuse, into the patient's mouth and beyond his/her teeth. In that way itacts as a bite protector and prevents the patient from inadvertentlybiting through the relatively soft material of the airway tube. Thepatient biting down onto the airway device and particularly orcompletely occluding airflow is a problem in certain procedures and withcertain patients. Secondly, the connector fits into a recess formedwithin the airway tube by the moulding process. In this way, theinternal surface of the airway tube 609 is substantially smooth anduniform. The internal diameter of the tube from the proximal opening inthe connector to the distal end where it opens out into the cuff issubstantially uniform. There is therefore no significant step change ininternal diameter at the inner end of the connector, which leads toimproved airflow and lower resistance to flow. This arrangement is shownparticularly in FIG. 32C being a section along line E-E in FIG. 32B.

In addition to the airway tube, the embodiments shown in FIGS. 23 to 26inclusive include a second passageway 540 that extends from an opening542 in the distal end of the device to an opening 541 in the proximalend of the device. This second, gastric tube passageway, is designed toallow an operator to pass a gastric tube down into the stomach of apatient without interrupting anaesthesia, during EMS or duringpre-hospital airway management. This second passageway also allows fordetection of any gastric aspirate in the event of passive regurgitationduring use. This second passageway must be large enough to allow a smallbore gastric tube to pass easily through the device. Typically a gastrictube passageway would be between 6 to 14 French gauge diameter.

The gastric tube passageway 540 and 640 shown in FIGS. 23 and 25 isshown housed substantially within the body of the airway device.However, it is also possible that this passageway could run externallyof the new main body, for example laterally or along the dorsal face ofthe device body.

Another feature of the passageways in these embodiments is that they aredisplaced to one side of the central longitudinal axis of the device, inthis case to the right-hand side of the central longitudinal axis, asviewed from the open face of the cuff. However, the passageway, which isoptional, could just as well exit along the mid-line or on the centrallongitudinal axis of the device as illustrated by 742 in FIG. 33.

A further embodiment is illustrated in FIG. 29. In this example alaryngeal cuff is formed around a pre-formed or pre-cut piece of airwaytube. This has the cost advantage that the airway tube may be formedfrom relatively inexpensive PVC tube or the like with a connector in oneend and the cuff moulded over the other end. Once again the airway tubemay be circular in profile or elliptical or any other profile asselected by the designer.

FIGS. 23B and 25B and 28B amongst others show the generally curvilinearshape of the device along its longitudinal axis. This shape is designedto correspond with the mouth/throat opening in an anaesthetised patient.Whilst the device is flexible it is resiliently deformable and tends toreturn to this concave/convex shape in its unstressed state.

In addition to passing tubes or other items through the gastric tubepassageway, it is possible to pass items such as a guide wire directlyinto the trachea through the airway tube. To facilitate this theinterior surface 650 of the cuff within the opening is ramped so as todirect a probe into the trachea (see FIG. 30C).

The device may be constructed from any suitable plastics material asselected by the materials specialist. Latex-free medical grade siliconerubber is one preferred material. The cuff should be soft in texture toavoid undue damage to the surrounding tissue. Other suitable materialsfor construction of this type of device include, but are not limited to,Poly Vinyl Chloride (PVC), Thermoplastic Elastomers such as the styrenicblock copolymers (eg Styrene Butadiene Styrene (SBS), Styrene EthyleneButylene Styrene (SEBS)), and Thermoplastic Olefin Blends (TPO),Thermoplastic PolyUrethanes (TPU), Thermoplastic Vulcanisates (TPV),Copolyester (COPE), Polyether Block Amides (PEBAX), Melt ProcessableRubbers, Flexible Co-polymers such as EVA, and foamed versions thereof,where appropriate.

A further important factor involved in the choice of a suitable materialis transparency. Ideally the material or materials of constructionshould be substantially clear or transparent. This enables theanaesthetist or operator to see the inner lumen of the airway to checkfor blockages or other problems. Such transparent materials are known tothe materials specialist.

By way of a preferred softness (hardness) range, on the Shore A scale ofHardness, a hardness of less than 30 for the face of the cuff thatcontacts the laryngeal inlet is optimum. By way of a preferred range, avalue on the same scale of between 0 to 20 is preferred, with aparticularly preferred range of 0 to 5. The apparent softness of thecuff can be further adapted by forming cavities or channels within thebody of the cuff itself.

In a further embodiment the cuff may be pre-filled with a fluid such asair, or other non-toxic gas, or a non-toxic liquid. In this context theterm fluid has a broad meaning and includes any suitable gas, liquid,vapour or mixtures or combination thereof and will be determined anddesigned by an expert in this field of anatomy/anaesthesia inconjunction with the materials specialist. The cuff will be constructedof such a material which will not allow nitrous oxide (anaesthetic gas)to diffuse through the material to any significant amount so that theextra luminal pressure is kept constant. It follows therefore that thecuff should be substantially impermeable to the fluid with which isfilled and to anaesthetic gases.

Alternatively, the cuff can be formed from a soft, foamed material orcan be foam filled. In either case this provides a soft deformable butshaped surface around the face of the cuff to engage over the anatomy ofthe laryngeal inlet region. Such a foam filled device will minimise anypotential damage to the structures in that region whilst still providinga substantially complete seal.

In the case of embodiments with a substantially circular airway tube anda gastric tube passageway which runs internally along the length of thedevice (as shown for example in FIGS. 23 and 24), the centre of the boreof the airway tube can be displaced to one side of the central ormid-line axis of the airway tube itself. This displacement providesspace for the gastric tube passageway to run alongside the bore of theairway tube. This arrangement is shown most clearly in FIG. 24D. Thegastric tube passageway is, in effect, housed within the outer body ofthe airway tube. This arrangement makes for a neat, streamlinedappearance in comparison to the arrangement in which the gastric tubepassageway is external to or mounted on the back of the device.

In terms of materials of manufacture and construction of an airwaydevice according to the present invention, it is advantageous to formthe front or open face of the cuff from a softer material than theremainder of the device. FIG. 23B shows a so-called “split line” 532between the softer plastics material on the face of the cuff andslightly firmer material on the dorsal or back part of the cuff 519. Theexact position of this split line may vary as determined by thedesigner. This line is shown in a slightly different position in FIG.31, where it is shown as feature 632.

By moving this split line towards the dorsal face of the cuff, thisensures that the sides of the cuff 533, 534 are also made of the softermaterial. The sides are therefore more easily deformed which contributessignificantly to the ease of insertion, and removal, of the cuff duringuse. The cuff squeezes and seals into the space above the laryngealinlet, cupping the laryngeal inlet to create a good seal forventilation. As the cuff reduces in width and squeezes into position,the airway opening increases in depth. This increase in depth reducesthe likelihood of the epiglottis occluding the airway duringventilation, a problem with prior art devices.

Turning now to methods of manufacturing airway devices generally, and inparticular airway devices according to the present invention, severalnew and cost-effective methods have been devised. These includeinjection moulding the device as single unit using a one-shot or atwo-shot process. Such methods also include extruding an airway tube andinjection moulding a cuff around the tube in a one-shot or two-shotprocess.

It follows therefore that the airway tube may be manufactured byextrusion or injection moulding and the cuff portion may be formed byone-shot or two-shot injection moulding.

Accordingly, one method of making an airway device according to thepresent invention is to provide a mould, the mould including interiorwalls which define the shape of the airway device, and injecting intosaid mould a molten thermoplastic compound. Once cooled the item isejected from the mould. In a further embodiment a two-shot process isused in which molten thermoplastic compound of a first hardness is firstinjected into the mould, which is retained in a pre-determined positionsuch that only a pre-determined portion of the mould is filled withpolymeric material. A second molten thermoplastic compound is theninjected into the remaining space in the mould to complete the injectionmoulding process. In this manner the relatively firmer airway tube anddorsal portion of the cuff can be formed first and the relatively softerface of the cuff can be formed in the second part of the operation.Alternatively the face of the cuff can be formed first and the remainderof the device is formed in the second part of the operation.

In an alternative method an airway tube is formed in a first step,either by extrusion or cutting a pre-determined length from a longerlength of tubing. A mould defining a hollow space which will become thecuff region in the finished product is then placed around the airwaytube and thermosetting plastic is injected into the mould in a one-stepor a two-step process.

In a third manufacturing embodiment a mould defining the cuff region isused to produce a cuff by either a one-step or a two-step injectionmoulding process. The cuff produced from this mould includes a recessadapted to accept an airway tube. In a separate operation or operationsan airway tube is formed by extrusion or in some other manner. Theairway tube is then inserted into and bonded to the recess provided inthe cuff for that purpose.

According to a further method of manufacture, the moulding process maybe used to mould not only the laryngeal cuff on to the end of apre-formed airway tube, but also a soft coating over the airway tubeitself. Whilst this requires a larger mould, and more plastics material,it has the advantage that the finished device has a uniform finish oversubstantially the whole of its outer surface. It is softer for thepatient and more aesthetically appealing for the operator. Having apre-formed airway tube running most of the length of the device gives adegree of resilience and rigidity which is particularly helpful whenusing very soft plastics material.

In terms of plastics materials used in these methods of manufacture,these will be determined by the materials specialist and are generallyonly limited by the ability to bond the chosen materials together. Byway of example only typically PVC can be used to mould the airway tube,the whole of the cuff region, the dorsal portion of the cuff region orany seals between these components. Polyolefins such as polyethylene andpolypropylene or a polyurethane can be used to form the airway tubeand/or the dorsal portion of the cuff region. A thermoplastic elastomeror a silicone rubber can be used to form the airway tube, the face ofthe cuff, the dorsal portion of the cuff, the whole of the cuff and anysecondary seals therebetween.

In this context the term “bond” has a particularly broad meaning. Itencompasses any method or process in which two or more parts arepermanently joined together. It includes, but is in no way limited to,molecular bonding, glueing using chemical adhesives, welding, includingultrasonic welding. The preferred method or methods of bonding will beselected by the materials specialist in this area.

The invention claimed is:
 1. A method of manufacturing an airway devicesuitable for human or animal use, said airway device comprising anairway tube having a distal end and a proximal end, the distal end ofwhich is surrounded by a non-inflatable laryngeal cuff, said methodcomprising the steps of:— (i) providing a mould, the mould includinginterior walls defining an interior volume which defines the shape ofthe airway device; (ii) introducing a liquid plastics material into thehollow interior volume of the mould; (iii) optionally introducing asecond liquid plastics material into said mould where it is requiredthat the airway device is made from materials of different Shorehardness; (iv) allowing the plastics material to solidify; (v) removingthe airway device from the mould.
 2. A method according to claim 1wherein said method also comprises the step of inserting into said moulda connector suitable for connecting to an anaesthetic gas supply, suchthat, after the moulding process is complete, the connector becomesattached to the airway device.